Communication networks consist of interconnected nodes and can be subdivided into core networks and access networks, the latter providing access to user equipment, for example a wireless access for mobile user equipment to a radio access network. Core networks interconnect access networks and further networks, e.g. other core networks or the Internet. In the Universal Mobile Telecommunications System (UMTS) architecture, an access network can be controlled by one or more Radio Network Controllers (RNC), which is connected to the core network and provides access to the core network, i.e. serves as access node. In the Global System for Mobile Communications (GSM) architecture, the access network can be controlled by one or more Base Station Controllers (BSC). The 3G core network is controlled by one or more Mobile Switching Centres (MSCs). These MSCs also influence the decisions in RNC and BSC.
For the transmission on a connection, speech (or other media) is compressed by encoding the speech (or the other media) according to one or more encoding/decoding schemes (and is subsequently decoded). Coding and decoding schemes are both referred to subsequently herein as coding schemes and alternatively denoted “codecs”.
Recent communication networks transport speech or other media using a packet based transmission. When applying packet based transmission a speech or media data stream is segmented into data portions constituting payload data of a data packet to which a packet header comprising addressing information of the data packet is attached.
When applying compression to the speech or media data payload, the fraction of the transmission bandwidth that is associated with the transmission of the packet headers, also termed the transport overhead, may become significant.
To address this problem different technologies have been developed to reduce the transmission bandwidth needed for the transmission of the packet headers. Transport header compression is a technology, wherein at a data source and a data sink an association between the a packet header and a packet header identifier is maintained and the packet header is replaced by its identifier at the data source, the data packet is routed along the transmission path using the packet header identifier, which is replaced by the associated packet header at the data sink. As the packet header identifier has a significantly smaller data size than the packet header itself, transmission bandwidth for transmitting the header identifier is also smaller. Packet header compression has been developed for IP (internet protocol), UDP (User Datagram Protocol), and RTP (real time protocol) as transmission protocols and standardised by the IETF (Internet Engineering Task Force).
Another solution to reduce the transmission overhead is to combine the payload data of multiple calls when transmitting the payload over a common transmission path portion. Also this solution has been standardised by the IETF. In the context of packet transmission this technology it is termed multiplexing.
Yet another solution is to adapt the amount of payload data which is transmitted from a particular data source to a corresponding data sink. By increasing the amount of payload transmitted within a single data packet the ratio between packet header size and the size of the payload of the data portion decreases, and by this the portion of the transmission bandwidth which is consumed for the transmission of the packet header is reduced accordingly. This solution to reduce the transport overhead is termed packetisation.
When increasing an amount of payload to be transmitted within a single speech or media data portion, the time represented by a single speech or media data portion increases as well. This time corresponds to the time needed to present the converted speech or media data to a listener and is termed the packetisation time of a speech or media data packet.
Applying packetisation can significantly reduce the transmission bandwidth, and the transmission costs, thus saving resources that are scarce in many telecommunication networks.
However, an increase of the packetisation time may affect the perceived communication quality.